Querysets are now lest restrictive when querying duplicate fields (#332, #333)

docs/changelog.rst

@@ -5,6 +5,7 @@ Changelog
 
 Changes in 0.8.2
 ================
+- Querysets are now lest restrictive when querying duplicate fields (#332, #333)
 - FileField now honouring db_alias (#341)
 - Removed customised __set__ change tracking in ComplexBaseField (#344)
 - Removed unused var in _get_changed_fields (#347)

mongoengine/queryset/visitor.py

@@ -26,6 +26,7 @@ class QNodeVisitor(object):
 class DuplicateQueryConditionsError(InvalidQueryError):
     pass
 
+
 class SimplificationVisitor(QNodeVisitor):
     """Simplifies query trees by combinging unnecessary 'and' connection nodes
     into a single Q-object.
@@ -39,6 +40,7 @@ class SimplificationVisitor(QNodeVisitor):
                 try:
                     return Q(**self._query_conjunction(queries))
                 except DuplicateQueryConditionsError:
+                    # Cannot be simplified
                     pass
         return combination
 
@@ -127,8 +129,7 @@ class QCombination(QNode):
             # If the child is a combination of the same type, we can merge its
             # children directly into this combinations children
             if isinstance(node, QCombination) and node.operation == operation:
-                # self.children += node.children
+                self.children += node.children
-                self.children.append(node)
             else:
                 self.children.append(node)
 

tests/queryset/visitor.py

@@ -68,9 +68,11 @@ class QTest(unittest.TestCase):
             x = IntField()
             y = StringField()
 
-        # Check than an error is raised when conflicting queries are anded
         query = (Q(x__lt=7) & Q(x__lt=3)).to_query(TestDoc)
-        self.assertEqual(query, {'$and': [ {'x': {'$lt': 7}}, {'x': {'$lt': 3}} ]})
+        self.assertEqual(query, {'$and': [{'x': {'$lt': 7}}, {'x': {'$lt': 3}}]})
+
+        query = (Q(y="a") & Q(x__lt=7) & Q(x__lt=3)).to_query(TestDoc)
+        self.assertEqual(query, {'$and': [{'y': "a"}, {'x': {'$lt': 7}}, {'x': {'$lt': 3}}]})
 
         # Check normal cases work without an error
         query = Q(x__lt=7) & Q(x__gt=3)
@@ -323,10 +325,26 @@ class QTest(unittest.TestCase):
         pk = ObjectId()
         User(email='example@example.com', pk=pk).save()
 
-        self.assertEqual(1, User.objects.filter(
+        self.assertEqual(1, User.objects.filter(Q(email='example@example.com') |
-                                Q(email='example@example.com') |
+                                                Q(name='John Doe')).limit(2).filter(pk=pk).count())
-                                Q(name='John Doe')
+
-                                ).limit(2).filter(pk=pk).count())
+    def test_chained_q_or_filtering(self):
+
+        class Post(EmbeddedDocument):
+            name = StringField(required=True)
+
+        class Item(Document):
+            postables = ListField(EmbeddedDocumentField(Post))
+
+        Item.drop_collection()
+
+        Item(postables=[Post(name="a"), Post(name="b")]).save()
+        Item(postables=[Post(name="a"), Post(name="c")]).save()
+        Item(postables=[Post(name="a"), Post(name="b"), Post(name="c")]).save()
+
+        self.assertEqual(Item.objects(Q(postables__name="a") & Q(postables__name="b")).count(), 2)
+        self.assertEqual(Item.objects.filter(postables__name="a").filter(postables__name="b").count(), 2)
+
 
 if __name__ == '__main__':
     unittest.main()